1. Field of the Invention
The present invention relates to a liquid crystal display device, and more particularly, to an array substrate and a liquid crystal display device using the array substrate.
2. Discussion of the Related Art
In general, the LCD devices include two substrates, each having electrodes that face each other, and a liquid crystal layer interposed between the electrodes. When a voltage is supplied to the electrodes, an electric field is generated to modulate light transmittance through the liquid crystal layer by reorienting the liquid crystal molecules, thereby displaying images. Among various types of LCD devices, active matrix liquid crystal display (AM-LCD) devices having thin film transistors (TFTs) and pixel electrodes arranged in matrix have been widely researched because of their superior resolution and capability to smoothly display moving images.
In a related art LCD device, a pixel electrode and a common electrode are positioned on a lower substrate and on an upper substrate, respectively. Thus, a longitudinal electric field is induced between the lower and upper substrates of the related art LCD device. This longitudinal electric field, which is perpendicular to the lower and upper substrates, drives liquid crystal molecules between the lower and upper substrates. Accordingly, the related art LCD device has superior light transmittance and aperture ratio. In addition, since the common electrode is grounded, breakdown of the liquid crystal cell is prevented.
FIG. 1 is an exploded perspective view of a liquid crystal display device according to the related art. In FIG. 1, a liquid crystal display (LCD) device includes a first substrate 22 and a second substrate 5, and a liquid crystal material 14 interposed therebetween. The first substrate 22 and the second substrate 5 face each other and are spaced apart from each other. A gate line 13 formed on the first substrate 22 crosses a data line 15 to define a pixel region “P.” A thin film transistor (TFT) “T” used as a switching element is connected to the gate line 13 and the data line 15 within the pixel region “P.” A pixel electrode 17 is also positioned in the pixel region “P” and connected to the TFT “T.”
A black matrix 6 having an open portion corresponding to the pixel region “P” is formed on the second substrate 5 and a color filter layer 7 including one of red, green and blue sub-color filters 7a, 7b and 7c is formed in the open portion. The color filter layer corresponds to the pixel electrode 17. A common electrode 18 is formed on the black matrix 6 and the color filter layer 7. The first substrate 22 having the TFT “T” and the pixel electrode 17 may be referred to as an array substrate and the second substrate 5 having the color filter layer 7 may be referred to as a color filter substrate.
FIG. 2 is a plan view showing a pixel region of an array substrate for a liquid crystal display device according to the related art. In FIG. 2, a gate line 13 is disposed along a first direction and a data line 15 is disposed along a second direction perpendicular to the first direction. Accordingly, the gate line 13 and the data line 15 perpendicularly cross each other. Since the gate line 13 and the data line 15 are formed of a metallic material having relatively high reflectance, an incident light reflects from the gate line 13 and the data line 15. The light reflecting from the gate line 13 and the data line 15 makes an interference pattern having a wave shape due to the periodicity of the gate line 13 and the data line 15. The interference pattern may be referred to as a moire phenomenon that deteriorates the display quality of the LCD device.